Your vehicle needs an oil change, and you take it to a local auto repair around the corner.  You leave the vehicle.  The business then informs you that, not only does your vehicle need an oil change, it also needs a new engine, and the repairs have begun without your SIGNED authorization, or a written estimate for the costs. 

Always look for the posted DMV Garage Registration, Business License and the Bill of Rights before you deal with any garage or repair shop.